Burless blanking machine and process

ABSTRACT

In a triple-action blanking press comprising a frame, a fixed die, a stripper, a clamping plate, a punch, a drive slide driving the punch and actuating means, the stripper can project from the die and an elastic member is interposed between the punch and the drive slide. The machine adjustment is such that during a first part of the machine cycle the stripper acts as a punch and the clamping plate as a die so that the piece is partially blanked on its punch side; during said operation the elastic member is completely compressed and the connection between the drive slide and the punch becomes rigid; then the punch acts just as a punch and forces the piece into the die until it is completely blanked. The operation provides completely burless blanked pieces.

O United States Patent 1 1 1111 3,878,746 Carmeli Apr. 22, 1975 [54]BURLESS BLANKING MACHINE AND 3.640.167 2/1972 Axtmann 83/623 x PROCESS3.739.669 6/1973 56kt 83/623 x [75] Inventor: Werter Carmeli, Milan.ltaly Primary M. Meisler [73] Assignee: International Business MachinesK Johnson Corporation, Armonk. NY. 122 Filed: 1161/. 23. 1973 [57]ABSTRACT In a tri le-action blankin press comprisin a frame. a Appl'4l8626 fixed die. a stripper, a cla mping plate, a pu nch, a drive slidedriving the punch and actuating means. the strip- [30] ForeignApplication Priority Data per can project from the die and an elasticmember is DCC. 22. 1972 Italy 33436/72 interPd between P and driveslide- The machine adjustment is such that during a first part of 52 us.(:1. 831/126; 33/51; 83/1 37; the machine cycle the stripper acts as aPunch and the 83/582; 33/616; 33,623 clamping plate as a die so that thepiece is partiall 1511 161. c1 B261 1/02 blanked its Punch side; duringSaid operation the [53] Field of Search H 83/7. 50 51 55 I37 elasticmember is completely compressed and the con- 83/623 M6 389. 542. 543.582. |26 nection between the drive slide and the punch becomes rigid;then the punch acts just as a punch and [56] Rderences and forces thepiece into the die until it is completely UNITED STATES PATENTS blanked.The operation provides completely burless blanked pieces. 3.l78.9754/l965 Gcorgcff 83/6l6 X 3.602.078 13/1971 Schindler 83/50 x 4 a s. 5Drawing gu s PATENTEDIPRZZISIS SHEU 1 0F 4 FIG. 1

PATENTEDAPRZZIQIS arm a or 4 FIG. 4

1 BURLESS BLANKING MACHINE AND PROCESS BACKGROUND OF THE INVENTION Thisinvention is directed to blanking apparatus and processes. moreparticularly to a line blanking apparatus and a process for blankingburless pieces with a fine blanking machine. In traditional blankingmethods tool assemblies are used comprising essentially a die and apunch which are mounted on a single-action press. The pieces blankedaccording to said methods present major surfaces which are neithercoplanar nor parallel to each other. and present lateral surfaces whichare very rough and non perpendicular to the major surfaces and havecranks whose depth depends on the hardness of the material.

Said pieces. which can be suitable for coarse productions. cannot beused in fine works without undergoing several further processings. It isknown in the art to obviate many of above-mentioned defects by usingspecial tool assemblies on triple-action presses. according to a processusually known as fine blanking."

However. even the fine blanking cannot prevent burrs from forming on thepunch side of the blanked pieces and that makes necessary to deburr theblanked pieces with suitable processings (e.g. sanding. tumbling. etc.).That does not represent a great disadvantage if the thickness of theblanked pieces is such to allow the cleaning operations without warpingor anyhow damaging the pieces themselves. It is however impossible totumble or sand very thin pieces. since said pieces are unavoidablywarped by said operations. An alternative to mechanical deburringconsists in chemical deburring. but it is so expensive to make theoperation uneconomic.

SUMMARY OF THE INVENTION Accordingly it is a main object of the presentinvention to provide a blanking method for making high precisioncompletely burless thin blanked pieces. Another object of the presentinvention is to provide blanked pieces which need no further cleaningoperation.

A still further object of the present invention is to provide animproved triple-action press for blanking high precision smooth finishthin pieces. These and other objects will be readily perceived from thefollowing description. claims and drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a fragmentary cross sectionalview of the triple-action press in accordance with the presentinvention.

FIG. 2 is a cross sectional view of the elastic member to be used in thepress in accordance with the present invention.

FIGS. 3. 4 and 5 show three different moments of the blanking cycle inaccordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT While the invention will bedescribed in connection with a preferred embodiment it will beunderstood that the invention is not limited to that embodiment.Referring now to FIG. I, the mount I is supported by the machine frame 2and in turn supports the die 3. The die 3 has a substantially flat outersurface 4 and is provided with a die aperture 5. The number 6 generallyindicates the stripper. which consists of a stripper body 7. a flange 8and a worksurface 9. The stripper body 7. which has a cross sectioncomplementary to the die aperture S, is partially nested in said dieaperture and is slid-ably guided by the walls which define it. Theflange 8 is slidably guided by the walls defining the chamber 10 in themount 1 and. since the diameter of the chamber 10 is greater than thediameter of the die aperture 5. said flange limits the downward movementof said stripper. The stripper 6 projects. in the position shown. fromthe outer surface 4 of the die 3. The stripper 6 is actuated by thehydraulic cylinder 11 through the ram 12.

The mount 13 of the clamping plate is supported by the base l4 and inturn supports the clamping plate 15. The clamping plate 15 has asubstantially flat outer surface 16 and is provided with an aperture [7which has the same cross section as the die aperture 5 and is alignedtherewith.

The base 14, slidably guided by means not shown. is vertically movableunder the action of the hydraulic cylinder 18.

The number 19 generally indicates the punch. which consists of a punchbody 20. a head portion 21 and a work surface 22. The punch body 20 hasa cross section complementary to the clamping plate aperture l7. inwhich it is partially nested. and is slidably guided by the wallsdefining said aperture.

The work surface 22 of the punch is. in the position shown. flush withthe outer surface of the clamping plate. The head portion 21 of thepunch I9 has a circu lar section and is slid-ably guided by the wallsdefining the chamber 23 in the mount l3. The plate 25 is fastened to thelower end of the punch head portion and engages an elastic elementconnecting said plate 25 to the plate 26, which in turn is secured tothe drive slide 24 vertically movable under the action of the main motor(not shown).

A cross section of the elastic member connecting the punch to the driveslide is shown in FIG. 2.

Said elastic member comprises an upper plate 25 to be fastened to thepunch. a lower plate 26 to be secured to the drive slide. a cup spring27, bushes 28, screws 29 and washers 30. The upper plate 25 comprises acentral body 31, a flange 32 provided with holes 33, and a member 34disposed on the upper side of the central body 31 which is apt to engagea recess in the punch. An annular recess 35 opens in the lower surface36 of the upper plate 25 and is coaxial with the plate itself.

The lower plate 26 is provided with threaded holes 37, in which screws29 engage, said holes being coaxial with the holes 33 in the flange 32.and further provided with the central threaded hole 40 which is able toengage a suitable member of the drive slide 24.

The cup spring 27 is nested in the annular recess 35 and engages boththe bottom surface 38 of said recess and the upper surface 39 of thelower plate 26. The bushes 28 are inserted into the holes 33 of theflange 32 and the screws 29 with the washers 30 fasten said bushes tothe lower plate 26. so that the upper plate 25 is reciprocably movablewith respect to the lower plate 26., said upper plate 25 being slidablyguided by the bushes 28.

The maximum spacing between the lower plate and the upper plate isdetermined by the length of the bushes 28. The working process formaking burless thin blanked pieces by a press according to the presentinvention will be described with reference to FIGS. 3. 4 and 5.

As previously stated. the burless fine blanking process requires atriple action press. The three machine actions actuate respectively thestripper 6a. the clamping plate 150 and the punch 19a and theirmagnitude and phase must be adjusted so that the following condi tionsare attained:

l. The action (the force on the stripper 60 must be sufficient toovercome the strain strength of the material to be blanked plus theforce exerted by the cup spring 27a.

2. The action on the clamping plate 150 must be greater than the actionon the stripper 6a.

3. The action on the punch 19a must be sufficient to overcome theblanking stress of the material to be blanked plus the actions on theclamping plate a and on the stripper 6a.

OPERATION The machine cycle can be divided into three main subcycleswhich we shall name first stroke." second stroke" and ejection andreset." Said three machine subcycles will be first briefly defined andthen described in details. The subcycle defined first stroke begins asthe machine starts; the machine is shown in its rest position in FIG. 3.During the first stroke the stripper 60 acts as a punch and the clampingplate 150 acts as a die. while the punch 19a acts as a blank holder (andfollows closely the piece to be blanked): this is a blanking strokeopposed to the usual one and the partial blanking depth on the punchside is equal to the initial distance between the two plates 25 and 26.

The second subcycle defined second stroke begins when the punch 19b hascompressed the spring 271) of the elastic member at its maximum and arigid connection between the punch 19b and the drive slide 24!; has beenachieved.

Through the rigid connection the drive slide 24b actuates directly thepunch l9h which penetrates into the material to be blanked overcomingthe opposite actions on the stripper 6b and on the clamping plate 15b.-this is the actual blanking stroke during which the material is forcedto enter the die 3b and is completely blanked. The third subcycle. thatwe have defined ejection and reset. begins when the punch 19b and thedrive slide 24h reverse their motion. During said subcycle the blankedpiece is ejected and the machine reset.

We shall now give a detailed description of the three subcyclespreviously defined. The machine is shown in its rest position in FIG. 3.The punch work surface 22a is substantially flush with the clampingplate outer surface 16a. The elastic member spring 270 has the maximumextension compatible with the elastic member adjustment; said adjustmentdetermines the depth of the partial blanking on the punch side. Thus theconnection between the drive slide 24a and 19a is of elastic kind. Thehydraulic cylinder 11a actuates the stripper 6a through the ram 12a.Said action is sufficient to overcome the strain strength of thematerial to be blanked, plus the force exerted by the spring 270 on thepunch 19a. The pressure in the hydraulic cylinder 18a is sufficient tobear the weight of the base 14a. of the mount 13a and of the clampingplate 15a.

Starting the machine. the drive slide 24a begins moving upwards drivenby the main motor through a double toggle mechanism (not shown in thefigures). Since the pressure in the cylinder 18a is sufficient to bearthe weight of the base and of the assembly it supports. the base 140.the mount 13a and the clamping plate will follow the movement of thedrive slide 24a. Likewise. since the elastic element 27a is able to bearthe weight of the punch 19a. the punch 190 will follow the upwardmovement of the drive slide. As a result. the drive slide 240, theclamping plate 150 and the punch 190 will move upwards, maintaining thesame position with respect to one another as in the rest position. Whenthe clamping plate outer surface 16a meets the material to be blanked.the action of the drive slide is transmitted to said material. which inconsequence is pushed upwardly toward the outer surface 40 of the die 3aand towards the work surface 9a of the stripper 6a. which projects outof the die 30. As the upper surface of the material to be blanked meetsthe work surface 9a of the stripper 6a the action of the hydrauliccylinder 18a on the base 14a and therefore on the clamping plate 15a issufficient to overcome the action on the stripper 6a. The action exertedby the elastic element 270 on the punch 19a is not sufficient toovercome the action on the stripper 60. As a consequence the clampingplate 15a continues its upward motion pushing that part of the materialto be blanked which does not face the work surface 9a of the stripper60, while that part of the material which faces the work surface 90 isstopped and forced to penetrate into the aperture of the clamping plate15a. Under the action ofthe stripper 60. which forces the material intothe aperture 170 of the clamping plate 15a, the punch [90 recedes withrespect to the clamping plate 150 and follows under pressure thematerial. while it is partially blanked. preventing the material frombending and in so doing altering the real dimensions of the perimeter soimpressed. Since the drive slide 24a continues moving upwards and thepunch 19a stands still. the elastic member spring 27a is compressed.

When the clamping plate 150 has clamped the material external to thefigure to be blanked against the outer surface 40 ofthe die 30. thefirst subcycle. i.e. the first stroke is completed. That part of thematerial which faces the work surface of the stripper has been forcedinto the clamping plate aperture for a depth essentially equal to theinitial distance between the plates 25 and 26 of the elastic member.Since said distance is less than the thickness of the material to beblanked. the material has been partially blanked on the punch side andthe edges of the partially blanked figure are rounded off. As shown inFIG. 4 the elastic member spring 27b is completely compressed and theplates 25b and 26b of the elastic member are in contact. The punch 19band the drive slide 24b are now rigidly connected and the secondsubcycle. i.e. the second stroke begins.

Since the drive slide 24b continues its movement upwards. the punch 19bis pushed upwards and since the clamping plate stands still. the punchslides through and out the clamping plate aperture 17b. The action onthe stripper 6b is not sufficient to bear the action of the drive slide24b, so that the punch 19b pushes the partially blanked part out of theclamping plate aperture 17b and, against the action of the stripper 6b.forces it into the aperture 5b of the die 3b blanking now the piece onthe die side. The machine is so preset that the piece is completelyblanked before the punch 19b penetrates into the aperture 5b of the die31). so that when the work surface 22b of the punch 19b is flush withthe outer surface 4b of the die 3b the motions of the punch 19b and ofthe drive slide 24b reverse and the return stroke begins.

In order to facilitate the separation of the material from the outersurface 4c of the die 3c. the pressure in the cylinder 11c. acting onthe stripper 6c and the pressure in the cylinder 18c acting on theclamping plate lSc are momentarily interrupted. The punch 19(- movesdownward and the pressure on the clamping plate c is reset. the punch19c continues moving downward and comes out of the blanked material.Before the punch 19c reaches the return stroke end also the pressureacting on the stripper 6c is reset. The material is caused to advance toanother work position and air blasts blow away the blanked piece. Whenthe punch reaches the return stroke end, the machine cycle is over andan identical cycle is ready to start.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof. it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

l. A blanking press comprising:

a frame;

a die. having a die aperture. said die being rigidly secured to saidframe;

a stripper disposed within said die aperture and slidably guided by saiddie aperture, said stripper projecting from the outer surface of saiddie during one predetermined period of the machine cycle;

a clam ping plate opposed to said outer surface of said die for clampingthe material to be blanked against said outer surface of said die, saidclamping plate being provided with an aperture. said aperture havingessentially the same section of and being essen- 6 tially aligned withsaid die aperture:

a punch disposed within said aperture of said clamping plate. said punchbeing slidably guided by said aperture;

a drive slide;

means for connecting said punch and said drive slide. said means beingable to maintain the work surface of said punch substantially flush withthe work surface of said clamping plate during another predeterminedperiod of the machine cycle. said means being further able to allow saidpunch to recede into said aperture of said clamping plate apredetermined distance after which said means supply a directtransmission of the motion of said drive slide to said punch;

means for actuating said stripper;

means for actuating said clamping plate; and

means for actuating said drive slide.

2. A blanking press according to claim I, wherein said means forconnecting said punch and said drive slide comprise essentially a firstplate secured to said punch. a second plate secured to said drive slideand a spring at least partially nested between said plates within asuitable cavity formed in said plates. so that said punch and said driveslide can approach compressing said spring until said plates meet andform a rigid transmission of the motion from said drive slide to saidpunch.

3. A blanking press according to claim 1, wherein said means foractuating said stripper is hydraulic means. said means for actuatingsaid clamping plate is hydraulic means and said means for actuating saiddrive slide is mechanical means.

4. A blanking press according to claim 1, wherein said stripper projectsfrom the outer surface of said die an amount which is less than thethickness of the material to be blanked.

1. A blanking press comprising: a frame; a die, having a die aperture,said die being rigidly secured to said frame; a stripper disposed withinsaid die aperture and slidably guided by said die aperture, saidstripper projecting from the outer surface of said die during onepredetermined period of the machine cycle; a clamping plate opposed tosaid outer surface of said die for clamping the material to be blankedagainst said outer surface of said die, said clamping plate beingprovided with an aperture, said aperture having essentially the samesection of and being essentially aligned with said die aperture; a punchdisposed within said aperture of said clamping plate, said punch beingslidably guided by said aperture; a drive slide; means for connectingsaid punch and said drive slide, said means being able to maintain thework surface of said punch substantially flush with the work surface ofsaid clamping plate during another predetermined period of the machinecycle, said means being further able to allow said punch to recede intosaid aperture of said clamping plate a predetermined distance afterwhich said means supply a direct transmission of the motion of saiddrive slide to said punch; means for actuating said stripper; means foractuating said clamping plate; and means for actuating said driveslide.
 1. A blanking press comprising: a frame; a die, having a dieaperture, said die being rigidly secured to said frame; a stripperdisposed within said die aperture and slidably guided by said dieaperture, said stripper projecting from the outer surface of said dieduring one predetermined period of the machine cycle; a clamping plateopposed to said outer surface of said die for clamping the material tobe blanked against said outer surface of said die, said clamping platebeing provided with an aperture, said aperture having essentially thesame section of and being essentially aligned with said die aperture; apunch disposed within said aperture of said clamping plate, said punchbeing slidably guided by said aperture; a drive slide; means forconnecting said punch and said drive slide, said means being able tomaintain the work surface of said punch substantially flush with thework surface of said clamping plate during another predetermined periodof the machine cycle, said means being further able to allow said punchto recede into said aperture of said clamping plate a predetermineddistance after which said means supply a direct transmission of themotion of said drive slide to said punch; means for actuating saidstripper; means for actuating said clamping plate; and means foractuating said drive slide.
 2. A blanking press according to claim 1,wherein said means for connecting said punch and said drive slidecomprise essentially a first plate secured to said punch, a second platesecured to said drive slide and a spring at least partially nestedbetween said plates within a suitable cavity formed in said plates, sothat said punch and said drive slide can approach compressing saidspring until said plates meet and form a rigid transmission of themotion from said drive slide to said punch.
 3. A blanking pressaccording to claim 1, wherein said means for actuating said stripper ishydraulic means, said means for actuating said clamping plate ishydraulic means and said means for actuating said drive slide ismechanical means.